October 15th Outside Nina Pham’s Apartment
One of the critical issues that emerged during the Ebola epidemic in Western Africa is how little we actually knew about the stability and persistence of the virus in the environment, and how that might vary across different climates and settings.
Variations in temperature, humidity, duration and strength of UV exposure, the types of fluids (including their pH), and the types of surfaces were all potentially mitigating factors.
Last August, a CDC Interim Guidance and FAQ (see Interim Guidance for Environmental Infection Control in Hospitals for Ebola Virus) had this to say about the research to date:
6. How long does the Ebola virus persist in indoor environments?
Only one laboratory study has been reported, which was done under environmental conditions that favor virus persistence. This study found that under these ideal conditions, Ebola virus could remain active for up to six days.1 In a follow-up study, Ebola virus was found, relative to other enveloped viruses, to be quite sensitive to inactivation by ultraviolet light and drying; yet subpopulations did persist in organic debris.2
In the only study to assess contamination of the patient care environment during an outbreak, conducted in an African hospital under "real-world conditions," Ebola virus was not detected by either nucleic acid amplification or culture in any of 33 samples collected from sites that were not visibly bloody. Virus was detected on a blood-stained glove and bloody intravenous insertion site by nucleic acid amplification, which may detect nonviable virus, but not by culture for live, infectious virus.3 Based upon these data and what is known regarding the environmental infection control of other enveloped RNA viruses, the expectation is that with consistent daily cleaning and disinfection practices in U.S. hospitals, the persistence of Ebola virus in the patient care environment would be short, with 24 hours3 considered a cautious upper limit.
That said, the CDC adopted some very strict guidance on dealing with potential environmental contamination from the Ebola virus, outlined in Interim Guidance for the U.S. Residence Decontamination for Ebola Virus Disease (Ebola) and Removal of Contaminated Waste and CDC Interim Ebola Guidance: Mortuary Removal and Handling.
Last February, in EID Journal: Post Mortem Stability Of The Ebola Virus, we saw a study that found that viable Ebola virus could be isolated 7 days post-mortem in cynomolgus macaques, and that viral RNA continued to be detectable reliably for 3 weeks and sporadically for up to 10 weeks.
The authors wrote, `. . . viable virus can persist for >7 days on surfaces of bodies, confirming that transmission from deceased persons is possible for an extended period after death.’
Today the same team of NIH researchers are back with another EID Dispatch, this time looking at the persistence of the Ebola virus in the environment.
Two of their most striking findings were;
- That the Ebola virus lived longer on surfaces (stainless steel, plastic, or Tyvek) roughly twice as long in a climate controlled environment (temp 21°C, 40% RH) than it did in a tropical environment (27°C, 80% relative humidity (RH)).
- The Ebola virus remains viable in water for as long as 3 days at 27°C or 6 days at 21°C
I’ve only excerpted part of the study, follow the link below to read it in its entirety.
Volume 21, Number 7—July 2015
Ebola Virus Stability on Surfaces and in Fluids in Simulated Outbreak Environments
Robert Fischer1, Seth Judson1, Kerri Miazgowicz, Trenton Bushmaker, Joseph Prescott, and Vincent J. Munster
Author affiliations: National Institutes of Health, Hamilton, Montana, USA
We evaluated the stability of Ebola virus on surfaces and in fluids under simulated environmental conditions for the climate of West Africa and for climate-controlled hospitals. This virus remains viable for a longer duration on surfaces in hospital conditions than in African conditions and in liquid than in dried blood.
We report stability of EBOV with a current outbreak strain from Guinea (Makona-WPGC07) (9) on 3 clinically relevant surfaces: stainless steel, plastic, and Tyvek (Dupont, Wilmington, DE, USA). We also determined the stability of EBOV in water, spiked human blood, and blood from infected nonhuman primates (NHPs). These experiments were conducted in 2 environmental conditions, 21°C, 40% RH, and 27°C, 80% RH, to simulate a climate-controlled hospital and the environment in West Africa, respectively.
We found that EBOV can persist on surfaces common in an ETU, highlighting the need for adherence to thorough disinfection and doffing protocols when exiting the ETUs and careful handling of medical waste. In addition, EBOV maintains viability for a longer duration in liquid than in dried blood. EBOV in blood of experimentally infected NHPs persists for a similar duration as EBOV in spiked human blood. A recent study showed that blood in the body cavity of an NHP contained viable EBOV for up to 7 days after death (13). We detected viable EBOV in drying blood for up to 5 days at both environmental conditions in human and NHP blood. Therefore, dried and liquid blood from an infected person in their home or ETU should be treated as potentially infectious. The finding that EBOV remains viable in water for as long as 3 (27°C) or 6 (21°C) days at the experimental concentration warrants further investigation into the persistence of the virus in aqueous environments, such as in wastewater or sewage canals. Viable EBOV has been isolated from urine (14) but not from human stool (8). Therefore, the potential for dissemination of EBOV through wastewater remains unknown.
This study is subject to several limitations. First, because standard volumes for samples were used, different volumes or matrices could influence the stability of EBOV under the tested conditions. Second, blood samples from the NHPs might have different immunologic or biochemical conditions, which can potentially influence virus stability. Third, the experimental conditions in the laboratory are sterile, but in disease-endemic areas and ETUs, bacteria or chemicals could influence EBOV viability.
Overall, we found that different environmental conditions, fluids, and surfaces influence the persistence of EBOV. These findings demonstrate that such factors are crucial in understanding transmission and improving safety practices.